277 
FXUS66 KPQR 101657
AFDPQR

Area Forecast Discussion
National Weather Service Portland OR
856 AM PST Mon Nov 10 2025

Updated aviation discussion.

.SYNOPSIS...A weak shortwave trough will bring light showers and
increased low to mid-level clouds to the region. Drier weather 
briefly returns on Tuesday as high pressure builds. A pattern 
change to cooler and wetter weather returns on Wednesday. Snow 
levels fall Thursday to Friday, returning chances for snow at 
the Cascade passes. Active weather continues into the weekend.

&&

.SHORT TERM...Today through Tuesday night...Radar and satellite
imagery as of early Monday morning depicts mid to high level 
clouds moving into northwest Oregon and southwest Washington as 
a weak front brushes the region. Prior to these clouds moving 
in, clear skies, calm winds, and a moist surface supported the 
development of dense fog in the southern Willamette Valley. 
Based on surface observations, dense fog is resulting in 
visibility of one quarter mile or less in this area. Therefore, 
a Dense Fog Advisory has been issued for the southern Willamette
Valley including Eugene, Creswell, and Cottage Grove through 10
AM this morning. If commuting, make sure to slow down, use your
low beam headlights, and leave plenty of distance ahead of you.

Circling back to the weak front that's moving in, some light 
showers have begun along the north OR and south WA coast, and
hi-res guidance suggests that these showers will gradually 
spread inland this morning. Since this weak front is tracking 
mostly to the north of us, most of the rain is being directed 
toward western Washington and southern British Columbia. Chances
for even receiving any measurable rain today (0.01" or more) 
is only 30-50% across the Willamette Valley and southwest WA 
lowlands based on the REFS. The wettest areas today would 
likely be along the south WA coast, and north OR/south WA 
Cascades and foothills where chances for receiving 0.10" of rain
or more are around 20-40%.

Easterly winds through the Columbia River Gorge have finally
begun to weaken as the pressure gradient from Troutdale (KTTD)
to The Dalles (KDLS) has eased to about -1 mb. Expect winds
today to be out of the south/southwest around 5 mph or less,
shifting more northwesterly this evening as weak surface high
pressure builds.

A shortwave ridge builds on Tuesday, briefly returning drier
conditions. However, an active weather pattern is in store for
the remainder of the week, which will maintain onshore flow 
with widespread precipitation and cooler temperatures (see long
term discussion).       -10

&&

.LONG TERM...Wednesday through Sunday...A deep upper level
trough over the NE Pacific will approach the Pacific Northwest
late Tuesday night into early Wednesday morning. A cold front
associated with this upper trough will push through the region
and bring widespread rain across northwest Oregon and southwest
Washington by Wednesday afternoon. There still remains 
uncertainty with the exact track and strength of the low, and 
thus precipitation amounts. For now, chances for 24 hour (4 PM
Wednesday to 4 PM Thursday) rain totals to exceed 1 inch are 
around 15-30% across interior lowland valleys, and 50-70% along
the coast and Coast Range.

Once this cold front pushes through, it will bring much cooler
air to the region on Thursday. Cooler air aloft will support a
more unstable atmosphere and thus lead to potential convection.
There is currently a 10-20% chance for thunderstorms on 
Thursday west of the Cascades, with the highest chances along 
the coast. Any passing thunderstorms could produce lightning, 
heavy downpours, gusty outflow winds, and small hail.

The majority of ensemble guidance also suggest that 850 mb 
(5000 ft) temperatures will fall to around -1 to -4 deg C
Thursday to Friday, which would result in snow levels falling 
to pass level in the Cascades. Current guidance suggests a 
70-80% chance that 48-hour snow totals between 4 AM Thursday to 
4 AM Saturday exceeds 6 inches at Santiam and Willamette Passes,
while chances are lower around 40-50% at Highway 26 near 
Government Camp. Those traveling to the Cascades at the end of 
the week should be sure to monitor the forecast and check on 
road conditions via ODOT/WSDOT before heading out.

Heading into Saturday, warmer air will be introduced as a warm 
front from another system approaches the Pacific Northwest. This
will briefly bring snow levels up above pass-level and maintain
wet weather through the weekend.        -10

&&

.AVIATION...At 17z Mon, a weak front is beginning to push inland 
from the northwest along the coast around the WA/OR border, and it 
will slowly move southeast through the day, reaching the Cascades by 
around 00z Tue. A scattered light showers will accompany the front 
north of a line from KTMK to KSLE. CIGs have fallen to IFR/MVFR 
along the coast with this front, and there is high confidence (>90% 
chance) that this trend will continue along the coast through 20-22z 
Mon north of KTMK and 00-03z Tue south of KTMK. Ahead of the high 
cloud cover associated with the front, areas of fog/mist and low 
stratus have developed across parts of the central and southern 
Willamette Valley, bringing LIFR/IFR CIGs and VIS. This trend will 
continue until the front makes its way into the Valley and brings 
more showers and mixing. This mixing will help dissipate any fog and 
improve VIS and CIGs to MVFR/low- end VFR thresholds. Guidance 
suggests a 60-80% chance for MVFR CIGs beginning with the frontal 
passage between now and 19z Mon for the northern Valley, and 18z Mon-
00z Tue for the central and southern Valley. After 00z Tue, 
conditions begin to trend more VFR for most terminals as the front 
exits the region, but coastal terminals maintain a 30-50% chance for 
IFR/MVFR CIGs. Generally south to southwest winds less than 5 kts.

Additionally, guidance is suggesting low stratus and fog potential 
in the Willamette Valley under clearing skies behind the frontal 
passage, developing around 05-08z Tue. Guidance suggests conditions 
will return to VFR between 10-12z Tue in the northern Willamette 
Valley as winds become more northerly. Conditions could remain 
lowered or fluctuate between VFR and MVFR/IFR through 14-18z Tue for 
the central Willamette Valley, and will likely remain lowered 
through 19-22z in the southern Willamette Valley.

KPDX AND APPROACHES...Prevailing MVFR ceilings expected as a frontal 
system moves through the area with light showers possible. Expect 
conditions to improve to VFR after 20-21z Mon as the front exits the 
region. MVFR/IFR ceilings could return again by 00-03z Tue. Easterly 
winds less than 5 kt today, turning more northwesterly after 00z 
Tue. -03

&&

.MARINE...Winds as of early Monday morning are southerly to
southwesterly around 5-10 kt as a weak front pushes through the
waters. Expect winds to gradually shift westerly this morning as
the front progresses inland. By this afternoon, weak high
pressure will rebuild and winds turn northerly. Seas generally 
remain 7-9 ft at 11 seconds today. Benign marine conditions 
continue through Tuesday night with variable winds and gusts 
remaining around 10 kt or less. High confidence (>95% chance) 
that seas remain below 10 ft through early Wednesday morning.

The next low pressure system in the NE Pacific will return
breezy  southerly winds and building seas Wednesday into 
Thursday, with high confidence for another period of conditions 
hazardous to small craft. As this system swings a front through 
the waters, we'll likely (60-80% chance) see frequent southerly 
wind gusts exceeding 21 kt and a >90% chance that seas build 
above 10 ft by Wednesday night. There is also a 40-60% chance 
for isolated gale-force wind gusts greater than 34 kt 
Wednesday-Thursday, with the highest chances across the outer 
waters beyond 20-30 NM. Active weather continues into the end of
the week with additional systems moving through the waters. 
                                                      -10

&&

.PQR WATCHES/WARNINGS/ADVISORIES...

OR...None.
WA...None.
PZ...None.

&&

$$

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